DECOMPRESSION DEVICE FOR INTERNAL COMBUSTION ENGINE TECHNICAL FIELD OF THE INVENTION The present invention relates to a decompression device for a lower compression pressure to allow easy starting when a four-stroke internal combustion engine is started. Previous Technology An example of a related valve gear is equipped with a camshaft supported in a freely rotatable manner through a pair of main bearings in the camshaft fastener attached to a cylinder head that uses a bolt, a pair of valve lifters to open and close the intake valve pair, a fixed rocker shaft and supported on a camshaft fastener having a shaft parallel to the axis of rotation of the camshaft and an oscillating arm supported on a freely balanced way on the same rocker. A pair of intake cams having the same prescribed cam surface, and a single exhaust cam having a prescribed surface positioned in a substantially central position between the legs.
intake cams that are then formed in the camshaft. The pair of intake cams makes sliding contact with the upper surfaces of the pair of valve lifters, the valve lifters slide according to the surface of the cam, and the pair of intake valves open and close at the prescribed time for open and close through the prescribed amount of elevation. A roller that makes roller contact with an exhaust cam is freely supported in a rotating manner on one side of the oscillating arm of the camshaft and a branch that divides in two is formed on the other side. The end of each of the branches makes contact with the surfaces of the upper end of the stems of the pair of exhaust valves and the two exhaust valves open and close in a prescribed time and through a prescribed amount of elevation in accordance with a surface of the exhaust cam. With the associated decompression devices, a centrifugal weight and a decompression cam linked to this centrifugal weight are provided on the outside of one of the bearings that support the camshaft, a camshaft arm.
decompression makes contact with one end of a shoe in order to play a sliding impulse at one end of the decompression cam, with one end of the branch section of the oscillating arm driven by the other end of the decompression arm, so that the Exhaust valve is driven in order to open and close for decompression. (For example, refer to patent document 1). [Patent Document 1) Japanese Patent Laid Open No. 2002-242631 (Figure 2). Problems to be Solved by the Invention When the decompression devices of the related technology, because the decompression cam is disposed on the outside of the bearings, a decompression cam is required to extend towards the tip of the branched part to drive the Exhaust valves to open and close from the decompression cam, the structure becomes more complex and the cylinder head also becomes larger. Therefore, the present invention provides for providing a decompression device that is simple in
structure and small in size. Elements and Effects for Solving Problems In order to solve the aforementioned problems, the present invention disclosed in Claim 1 is a decompression device for an internal combustion engine equipped with inlet valves and exhaust valves having an internal combustion engine. cylinder head arranged with a pair of right and left camshaft bearings sandwiching the intake valves and exhaust valves, comprising a camshaft having cam projections of at least one pair of intake cams between the side bearings of the camshaft corresponding to the pair of the right and left bearings, and a decompression element with a decompression cam with a centrifugal weight disposed at one end of the camshaft that passes through the crunch near the end of the camshaft so that a tip thereof is disposed in the vicinity of the projections of the cams, with the decompression element comprising the centrifugal weight, the decompression cam and a rotating arrow that couples the centrifugal weight and the decompression cam in an integral manner.
As described above, in the present invention, a centrifugal weight is disposed at one end of the camshaft and the end of a decompression cam linked to the centrifugal weight through a rotary shaft that is passed through the bearing near the end. of the camshaft to be arranged close to the projections of cams. The decompression arm of the related technology is therefore no longer required, the structure is simplified and the cylinder head can be made smaller. In the aspect of the invention as disclosed in Claim 2, with the decompression device for an internal combustion engine as disclosed in Claim 1, a power transmission element for transmitting power from the arrow of the crankshaft to the shaft of the cams are provided on the outer side of one of the bearings of the pair of the right and left camshaft bearings, the projection of the intake valve cam of the intake / exhaust camshafts are provided near the bearing in the opposite side of the side where the power transmission element was installed, and the pair of bearings supporting a rotary arrow of the power element.
Decompression is formed divided towards the projection of the cam of the left and right intake valve. As described above, bearings that support a rotary arrow of the decompression element are formed with spacings positioned to the left and right of the projections of the cams. Therefore the interval between the bearings can be kept wider and the durability of the decompression device can be improved. In the aspect of the invention as disclosed in Claim 3, with the decompression device for an internal combustion engine of Claim 2, a bearing element with an internal diameter and a common external diameter is provided between the cylinder head. and the camshaft. Therefore the present invention allows the bearing elements to become common, the types of parts can be reduced and the ease of assembly can be improved. MODES OF CARRYING OUT THE INVENTION Figure 1 is a cross-sectional view of a valve chamber for an engine of
internal combustion with which each of the embodiments of the present invention relates. The internal combustion engine to which the decompression device of the present invention is applied is a cycle internal combustion engine with four alternating single cylinder journeys of the overhead camshaft type mounted on a motorcycle. An arrow F designates the front direction when the internal combustion engine is mounted on the vehicle. A valve chamber 3 is formed between a cylinder head 1 coupled to an upper end surface of a cylinder block (not shown) into which the pistons (not shown) are inserted so as to move freely in an alternating manner in a cylinder head cover 2 coupled to a surface of the upper end of the cylinder head 1. A combustion chamber 4 is formed between the bottom surface of the cylinder head 1 and the pistons. An intake port 5 for the head of the cylinder 1 is formed in the rear part of the vehicle (left side in Figure 1), and the branches in two in order to form a stop of intake openings 6 opening in the chamber of combustion 4.
An exhaust port 7 of the head of the cylinder 1 is formed towards the front of the vehicle (right side in Figure 1), and the branches in two in order to form a pair of exhaust openings 8 opening in the chamber of combustion 4. A pair of intake valves 9 for opening and closing the intake openings 6 and a pair of exhaust valves 10 for opening and closing the exhaust openings 8 are freely slidable in the valve liners 11, 12 press fit on the cylinder head 1. The intake valves 9 and the exhaust valves 9 are driven so that when closing the intake openings 6 and the corresponding exhaust openings 8 they use spring force of the springs of the valve 13, 14. An intake tube (not shown) is connected to a caudal side above the intake port 5, and a carburetor (not shown) to form a fuel / air mixture provided in the combustion chamber 4 that fits on the end of the intake tube. An exhaust pipe (not shown) for removing the combustion gas from the combustion chamber 4 is connected to an opening on the side of the opening downstream of the exhaust port.
Figure 2 shows the interior of the valve chamber as viewed from above by removing the cylinder head cover from the internal combustion engine. A description is now presented with reference to Figure 1 and Figure 2, The valve assembly stored in the valve chamber 3 comprises a lower camshaft holder 15 formed in the head of cylinder 1 so as to divide vertically in two from the position of the central line of the camshaft, an upper camshaft fastener 16 fastened to the lower camshaft holder 15 using a bolt 17, a camshaft 20 supported in a way that rotates freely to Through a pair of main bearings 18, 19 of the common internal diameter, a pair of valve lifters 21 for opening and closing the intake valve pair 9, a rocker shaft 22, having an axis parallel to the axis of rotation of the camshaft 20, and which is supported in a fixed manner by the fasteners of the upper and lower camshaft 15, 16 and an oscillating arm 23 supported in a freely sliding manner in the same axis d and rocker 22. The camshaft 20 is driven rotationally by the pistons and has a shaft of
rotation parallel with the axis of rotation of the arrow of the crankshaft. A camshaft 20 is rotationally driven at a rotational speed that is half the arrow of the crankshaft as a result of the power of the crankshaft arrow through a timing chain that passes a driving sprocket coupled to the arrow of the crankshaft. crankshaft and a driven gear 26 coupled to the left end of the camshaft 20. A pair of intake cams 27, 28, having the same prescribed cam surface and a single exhaust cam 29 having a prescribed cam surface positioned substantially in the center of the intake cams 27, 28. The pair of intake cams 27, 28 make sliding contact with an upper face of the elevators of the valves 21 adjusted so that they slide freely within a guide tube 30 (FIG. 1) formed in the head of the cylinder 1, with the elevators of the valve 21 sliding according to the surface of the cam, with the pair of inlet valves 9 opening and closing in a time to open and close and a prescribed amount of elevation. A roller 31 that makes contact rolling with an exhaust cam 29 is supported in a manner
rotating freely by a roller shaft 32 on one side of the camshaft 20, with two-way branches 23a and 23b forming on the other side. The ends of each of the branches 23a, 23b 5 contact the end surfaces of the valve 10a of the pair of exhaust valves 10. The exhaust cam 29 causes the oscillating arm 23 to oscillate through the contact roller 31. according to the surface of the cam, and the two exhaust valves 10 are opened and closed at the prescribed times and by the prescribed lifting amounts. Figure 3 is a vertical cross-sectional view of the portions comprised
of the camshaft 20 shown in Figure 2, the driven gear 26 linked to the camshaft 20, and the main bearings 18, 19, etc. An insertion hole of the decompression element 40 is provided in the camshaft
parallel to the axis of rotation 20, and a decompression element 41 that is inserted so that it freely rotates therein. The details of the shape of the decompression element 41 are described in detail below, but comprise a weight
centrifuge 42, a decompression cam 43, a
rotary arrow 44 formed integrally coupling the centrifugal weight 42 and a decompression cam 43. The decompression element is prevented from sliding through a slip prevention plate 46 held by a bolt 45 to the end of the shaft of cams 20. Each of the projections of cams of each of the intake cams 27, exhaust cams 29 and intake cams 28 are provided between the pair of main bearings
18, 19 in order from the right side. A through hole 27a provided in the cam projection on the intake cam 27 is a hole used to decide a relative position in the direction of rotation at the moment of coupling the camshaft
and the driven gear 26. Figure 4 is a vertical cross-sectional view of the camshaft 20 shown in Figure 3. In the drawings, an orifice containing a decompression cam 48 is formed in the
The rear end of the insertion hole of the decompression element 40 and the decompression cam 43 is contained in the hole containing the decompression cam 48. A pin hole in the right end of the camshaft 20 is
an insert hole 47 for a clamping bolt
of plate 45 for securing the slide prevention plate 46. A funnel-shaped hole in the center of the left end surface of the camshaft 20 is a coupling hole 50 for a rotation prevention stop which is part of a slide prevention plate 46. The left end of the camshaft 20 constitutes a stop 51 with which the centrifugal weight 42 of the decompression element 41 comes into contact at both ends of the range or rotation. A roe section 20a is provided in the central part of the camshaft 20 to ensure lightness in the weight. A view taken along V of Figure 4 is shown in Figure 5, a cross-sectional view taken along VI-VI of Figure 4 is shown in Figure 6, a cross-sectional view as shown in FIG. The length of VII-VII of Figure 4 is shown in Figure 7, a cross-sectional view taken along VIII-VIII of Figure 4 is shown in Figure 8, a cross-sectional view taken along the length of - X in Figure 4 is shown in Figure 10, a view along XI of Figure 4 is shown in Figure 11. As can be seen from Figure 4, the
Figure 9 and Figure 11, a flat bottom surface 48a is formed in the bottom of the hole 48 that contains the decompression cam formed by making a hole in the part of the exhaust cam 29. The decompression cam then appears frequently from an opening 48b (Figure 9) of the orifice containing the decompression cam 48. As can be seen from Figure 4, Figure 5 and Figure 6, a stop 51 for the centrifugal weight 42 of the decompression element 41 for contacting the two ends of the rotation range that are formed at the right end of the camshaft 20. Figure 2 is an elongated vertical cross-sectional view of the decompression element 41 shown in Figure 3. Figure 13 is a viewed along XIII of the centrifugal weight 42 of Figure 12 seen from the right side. Figure 14 is a cross-sectional view along XIV-XIV of the decompression cam of Figure 12. The centrifugal weight 42 and the decompression cam 43 are coupled through the rotary arrow 44 of the circular cross-section formed integrally with these portions. The decompression cam 43 is equipped with a decompression actuation surface 43a which
it consists of the same curved surface as that of the surface of the outer cylinder 43x and an exhaust surface 43d formed through cutting part of the exterior of the decompression cam 43. The relation between the relative position of the decompression cam 43 with respect to to escape cam 29 and the actions of each of the surfaces are described below. Figure 5 is a view showing the camshaft 20 and the centrifugal weight 42 as seen from the right side of the camshaft 20. The slide prevention plate of the decompression element 46 is omitted from the drawings in order to avoid that the drawings are complicated. Figure 16 is a view taken along XVI of Figure 15. A coil spring 52 is provided on the rotary arrow 44 of the decompression element. The coil spring 52 drives the centrifugal weight arm 42 in the direction of the surface of the stop 512 at the time of low speed rotation of the stop 51 shown in Figure 15 when the internal combustion engine is stopped. Figure 15 and Figure 16 show the situation when the camshaft 20 rotates at a lower speed lower than the rotational speed of the camshaft 20.
release of the decompression operation established when adjusting the coil spring force of the coil spring 52 or stops. When the driven gear 26 rotates in accompaniment of the rotation of the crankshaft arrow, the camshaft 20 rotates in the direction of the arrow W. When the camshaft 20 rotates at a rotational speed lower than the rotational speed set as described above, a side surface 42a of the arm comes into contact with the surface of the stop 51a at the time of the low speed rotation of a side surface of the stop 51 and enters high due to the driven force of the coil spring 52 as is shown in Figure 15. Figure 17 is a view of the camshaft
and the centrifugal weight 42 seen from the right of the camshaft 20 when the rotational speed of the motor is increased so that the camshaft 20 rotates at a high speed higher than the rotational speed of release of the decompression operation set as described above. When the centrifugal weight 42 rotates relatively relative to the camshaft 20 exceeds the rotational speed due to the application of the centrifugal force, an end portion 42b of the
The arm on the side opposite to the weight of the centrifugal weight 42 is then stopped in a position to make contact with the surface of the stop 51b at the time of the high speed rotation on a side surface other than that mentioned above of the stop 51. In this example, the centrifugal weight 42 is rotated through ninety degrees and then stopped. Figure 18 and Figure 19 show the relative positional relationships of the exhaust cam 29, the centrifugal weight 42 and the decompression cam 43, with Figure 18 showing the situation when the camshaft 20 is rotated at low speed and Figure 19 shows the situation when the camshaft 20 rotates at high speed. The centrifugal weight 42 and the centrifugal weight 42 are interspersed, and therefore their relative positional relationships do not change with the rotation of the backward front of the centrifugal weight 42. When the centrifugal weight 42 rotates, the relative potion ratio of the cam of decompression 43 and the exhaust cam 29 changes. When the camshaft 20 rotates at low speed as shown in Figure 18, the decompression action surface 43a formed by a portion of the cylinder-shaped outer surface 43x of the decompression cam is projected.
out and then the outer surface of exhaust cam 29a. This then pushes the roller 31 (Figure i) of the oscillating arm 23 upwards, and the exhaust valves 10 are opened and closed for decompression in the times for opening and closing and the prescribed lifting quantities. The decompression cam 43 is subject to the pushing force from the roller 31 when the roller 31 contacts the decompression actuating surface 43a. A support surface of the decompression cam 43c formed on the opposite side of the decompression actuating surface 43a of the decompression cam 43 comes into contact with the flat bottom surface 48a of the orifice 48 containing the decompression cam. The support surface of the decompression cam 43c is a surface formed from the part of the outer cylinder surface 43x of the decompression cam. The combination of the support surface 43c of the decompression cam and the flat bottom surface 48a constitute a type of bearing. When the rotary speed of the motor is increased so that the camshaft 20
a velocity can rotate, the decompression cam 43 operating in unison with the centrifugal weight 42 rotates relatively with respect to the camshaft 20, that is, with respect to the exhaust cam 29 and the state shown in FIG. Figure 19. The decompression release surface 49b formed by a cut of the part of the outer surface of the decompression cam 43 in order to coincide with the outer surface of the exhaust cam 29a then faces in the direction of the opening 48b of the orifice containing the decompression cam 48. The release surface Decompression means -43b does not project further outwards than the outer surface of the exhaust cam 29a and the decompression cam 43 therefore can not be pressed by the roller 31 of the oscillatory arm 23. As a result, the action of decompression is released. The exhaust surface 43d formed by cutting a portion of the outer surface of the decompression cam 43 is formed on the opposite side of the decompression relief surface 43b of the decompression cam 43. The decompression release surface 43b it does not project towards
out more than the outer surface of the exhaust cam 29a when the camshaft 20 is rotating at high speed, and the thrust force is not applied from the roller 31 on the decompression cam 43. When the camshaft 20 rotates at low speed, the type of bearing configured from a combination of the support surface of the decompression cam 43c and the flat bottom surface 48a is not required. When the decompression cam 43 rotates from a rotation potion at low speed to a rotational speed rotation position, it is necessary for the rotation to be effected smoothly. Because of this, the exhaust surface 43d is formed and it is ensured that the decompression cam 43 does not contact the flat bottom surface 48a of the hole containing the decompression cam 48 to reduce the frictional resistance. As described above, in this embodiment, the centrifugal weight 42 is disposed at the end of the camshaft 20, and the decompression cam 43 is coupled to the centrifugal weight 42 through the rotary shaft 44 arranged to pass through the bearing 18 near the end of the camshaft 20 and extend as much as the projection of the exhaust cam 29. Therefore, it is not necessary
a decompression arm as in related technology that extends from the position of the decompression cam to the tip of the oscillating arm. As a result in this embodiment, the structure is simplified and the cylinder head can be made small. In this embodiment, the bearing 44a (Figure 3, Figure 12 = support the rotary arrow 44 at the right end of the rotary arrow 44 of the decompression element, and the type of bearing (Figure 18) supports the decompression cam 43 configured from the support surface of the decompression cam 43c and the lower surface 48a of the orifice containing the decompression cam 48 is formed so that it is spaced apart on the left side and the right side of the cam projection of the In this way, the range of the bearing can maintain substantial and the durability of the decompression device is improved.The camshaft fastener of this embodiment is in the form of a fastener divided into two upper and lower parts on and below the position of the centerline of the camshaft 20, of the camshaft fastener
lower 15 formed in the head of the cylinder 1 and the upper camshaft holder 16 fastened with the bolt 17. Therefore the camshaft 20 can be supported by the pair of main bearings 18 and 19 having in common internal and external diameters . Therefore, the bearing elements can be made common, the types of parts can be reduced and the ease of assembly can be improved. The decompression cam 43 of this embodiment is such that the roller 31 comes into direct contact with the decompression cam 43 in combination with the exhaust cam 29 touching the roller 31 of the oscillating arm 23. Therefore, at one point of difference from the structure in the related technology where contact with the decompression cam was made by a shoe. Therefore, the projection of the cam of the decompression cam may be smaller, and this contributes to making the bearing to support the decompression cam smaller. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 in a vertical cross-sectional view of a valve chamber for an internal combustion engine with which each of the embodiments of the present invention is related.
invention Figure 2 shows the interior of the valve chamber seen from above with the cover of the cylinder head of the internal combustion engine removed. Figure 3 is a longitudinal cross-sectional view of a camshaft and portions linked to this camshaft. The Figure < 3 is an enlarged cross-sectional view of the camshaft. Figure 5 is a view along V of Figure 3. Figure 6 is a cross-sectional drawing along VI-VI in Figure <;3. Figure 7 is a cross-sectional drawing along VII-VII in Figure 4. Figure 8 is a cross-sectional drawing along VIII-VIII in Figure A. Figure 9 is a cross-sectional drawing along IX-IX in Figure 4. Figure 10 is a cross-sectional drawing along XX in Figure 4. Figure 11 is a view along the XI of Figure 4. Figure 12 is a sectional view
elongated cross section of the decompression element. Figure 13 is a view along XIII of Figure 12. Figure 14 is a cross-sectional drawing along XIV-XIV of Figure 12. Figure 15 is a view showing the camshaft and the elements linked to the camshaft from the right side of the camshaft and shows the decompression position of the light tree element during the stop and during the low speed rotation. Figure 16 is a view along the arrow XVI of Figure 15. Figure 17 is a view showing the camshaft and the elements linked to the camshaft from the right side of the camshaft and showing the Decompression position of the camshaft element during low speed rotation.
Figure 18 is a view showing the positional relationship of the exhaust valves, the decompression cam and the centrifugal weight, and shows the position during the low speed rotation of the camshaft. Figure 19 is a view showing the positional relationship of the exhaust valves of the
Decompression cam and centrifugal weight and shows the position during the high-speed rotation of the camshaft. DESCRIPTION OF NUMBERS 1 cylinder head, 2 cylinder head cover, 3 valve chamber, 4 combustion chamber, 5 intake port, 6 intake opening, 7 exhaust port, 8 exhaust opening, 9 intake valve , 10 exhaust valve, 10a upper end surface of exhaust valve system, 11 valve sleeve, 12 valve sleeve, 13 valve spring, 14 valve spring, 15 lower camshaft fastener, 16 tree fastener upper side cam, 17 bolt, 18 main shaft bearing, 19 main shaft bearing, 20 camshaft, 20a hollow section, 21 valve lifter, 22 rocker arm, 23 oscillating arm, 23a branch, 23b branch, 26 driven sprocket, 27 inlet cam, 27th through hole, 28 inlet cam, 29 exhaust cam, 29a outside surface of the exhaust cam, 30 guide tube, 31 roller, 32 roller arrow, 40 hole insert of the element decompressor, 40 41 decompressor element, 42 centrifugal weight, 42a arm side surface, 42b
end of the arm on the side opposite the weight, 43 decompression cam, 43x outer cylinder surface of the decompression cam, 43a decompression actuating surface, 43b decompression release surface, 43c decompression cam support surface, 43d exhaust surface, 44 rotary arrow, 44th bearing for rotary arrow, 45 bolt, 46 slide prevention plate of the decompression element, 47
bolt hole fastener of the slide prevention plate, 48 hole containing the decompression cam, 48a flat bottom surface, 48b opening, 50 stop hole for prevention of rotation of slip prevention plate,
51 stop, 51a stop surface for low speed rotation time, 51b stop surface for high speed rotation time, 52 coil spring.